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Effects of Anesthesia on the Heart

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I am a board-certified anesthesiologist in Lake Tahoe, California. I write from the perspective of both a doctor and a patient.

Heart rate and rhythm are monitored during anesthesia. The overall function of the cardiovascular system is also indicated by the blood pressure and oxygen level on the monitor.

Heart rate and rhythm are monitored during anesthesia. The overall function of the cardiovascular system is also indicated by the blood pressure and oxygen level on the monitor.

Anesthesia Affects Heart Function

Different types of anesthesia affect the heart in different ways. As a board-certified anesthesiologist, I see these effects each and every day on healthy and sick hearts. Anticipating and understanding these issues is important to the successful delivery of anesthesia.

In most cases, and with most anesthesia regimens, the overall effect will be to depress heart function. The physiology of the heart is complex, as is the pharmacology of anesthetic medications. This means that sometimes the effects will be unpredictable, and there will always be exceptions to every rule.

Note: Anesthesia here will refer to general anesthesia, where unconsciousness is achieved and maintained during surgery.

Video: Good Introduction to Normal Heart Function

The Heart: Anatomy and Physiology Basics

The heart is often referred to as a four-chamber pump. Blood returns from the body to the right side of the heart. It then goes to the lungs to get filled with oxygen. The oxygenated blood then flows to the left side of the heart to be pumped out to the body to deliver that oxygen.

In order to be an effective pump, the heart functions through an intricate and ordered interplay of electric signals, muscle contractions and one-way valves.

The self-generated electrical signals send a wave of current down special conducting fibers in a specific pattern. This triggers certain parts of the heart muscle to contract in an ordered manner. This wave of contractions squeezes blood out of each ventricle (large pumping chamber), through valves that open and allows blood to return to the atria (collecting chambers). The strength of contraction ensures that most of the blood in the chamber is squeezed out with each heart beat.

Any disruption in this pattern can affect heart function. Anesthesia can interrupt this pathway in several different ways.

In discussing the cardiac implications of anesthesia medicines, usually, we either have a drug and wonder about its effects on the heart, or we have specific effect and want to know which drugs can cause it. Both approaches are presented below to make the information easier to find. Only the most typical examples of the most common anesthesia drugs are presented as a thorough discussion would require textbook length consideration.

Cardiac Effects of Common Anesthetic Agents

The table below gives examples of some common individual anesthetic agents and their heart effects. Keep in mind that for each effect, there is likely a study or two that disputes the findings. The data here are consistent with the current edition of the authoritative text, Miller's Anesthesia (7ed., 2009). The conflicting conclusions show how complex these interactions are, and how the education and experience of the anesthesia provider helps keep us safe during anesthetics.

  • Propofol, etomidate and pentothal are "induction" agents used to get patients to sleep.
  • Ketamine is a unique drug that may be used for sedation, as well as induction and maintenance of anesthesia.
  • Fentanyl and morphine are pain medicines used before, during and after surgery.
  • Succinylcholine is a muscle relaxant that makes placement of the breathing tube and surgery easier to achieve.
  • Halothane, isoflurane and sevoflurane are anesthesia gases used to keep patients asleep for surgery, delivered through a breathing tube or mask.

This is NOT a comprehensive list of anesthetic agents; these are examples only. Likewise, the effects may vary depending on a large number of factors and interactions. No clinical practice advice is implied, nor should this chart be used for such.

 Heart RateHeart RhythmContractility

Propofol

no significant change to decreases at higher doses

little effect, potential benefit in slowing heart rate in some fast arrythmias

little effect to ability to decrease cardiac output at higher doses

Pentothal

increases by 10-40%

potential disruption, prolong QT interval

decreases cardiac output

Etomidate

mimimal effect

minimal effect

minimal effect

Ketamine

increases

no specific changes

increases

Fentanyl

decreases

variable, but overall may prevent some arrhythmias

little change to mild increase

Morphine

decreases

variable, but overall may prevent some arrhythmias

uncertain, may be similar to fentanyl

Succinylcholine

variable, usually decreases especially at usual doses and after a second dose

increases likelihood of several kinds of arrhythmias

decreases at usual doses

Halothane

no change to little change

increases likelihood of arrythmias

decreases

Isofllurane

decreases

potential changes, but of unknown significance

decreases

Sevoflurane

decreases

potential changes, but of unknown significance

decreases

Anesthesia Machine and Monitor

IV and inhaled agents are combined to deliver a general anesthetic, in most cases.

IV and inhaled agents are combined to deliver a general anesthetic, in most cases.

Effects of Anesthesia on the Heart Vary

The effect that anesthesia has on the heart is influenced by

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  • Preoperative heart function
  • Any heart disease including blockages in arteries (coronary disease), valve problems, high blood pressure,
  • The type of anesthesia
  • The specific medications used during anesthesia
  • Medications taken by the patient
  • Other coexisting disease

Overall Effect of General Anesthesia on Heart Function

There are many cardiac parameters to consider when giving an anesthetic. Most commonly, we may be concerned about the effect of anesthesia on heart rate, heart rhythm and the strength of pumping action of the heart (contractility). The described effects are very broad generalizations, only.

In reality, multiple agents in combination are used for each anesthetic on a patient, so it is often difficult to predict or know which drug is causing the predominant effect. In addition, anesthesiologists can use these medications in varying amounts, dosages and combinations to achieve, or prevent, a certain effect on the heart.

Anesthesia Effects on Heart Rate

A human's resting heart rate is determined by numerous and complex factors. Any stress on the body will usually cause an increase in heart rate, and this can include surgery and anesthesia.

  • Induction agents tend to allow increased heart rate in low doses and slowed heart rate in higher doses.
  • Narcotic pain medicines tend to slow heart rate (except for meperidine which increases heart rate).
  • Succinylcholine will decrease heart rate. This can actually be dangerous in certain situations and must be monitored closely in those at risk.
  • Anesthesia gases have variable effects, influenced by many factors.

Anesthesia and Heart Rhythm

Many anesthetic agents have the potential to cause irregular heart rhythms. Patients with pre-existing arrhythmias and abnormal blood electrolytes (calcium, magnesium, potassium) are most at risk. In addition, a patient's medications influence the potential for arrythmias, as well.

effects-of-anesthesia-on-the-heart

Anesthesia Effects on Contractility

Overall, general anesthesia at levels high enough to maintain unconsciousness, will decrease the strength of contraction. Individual medications have variable effects as seen in the above table.

This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Comments

Mary on April 12, 2019:

in September I had outpatient shoulder surgery ended up lasting for hours I told Anastasia I was just I get very sick from anesthesia when I woke up I was violently ill my heart rate was down to 3 to 5 beats a minute they ended up putting me in ICU it's been almost nine months now and I still don't feel good I've gained significant weight I'm listless tired my ankles and body or swelling is this possible that I have some long-lasting effects I explained to the anesthesiologist how sick I get and he seem to not really get it I'm scared I was overdosed in injured my kidneys